Kursk war videos: How Russian soldiers walked 15 kilometres inside gas pipeline to ambush Ukrainian positions! WATCH HERE

Revealing the thrilling details of its men's valiant offensive, Russia said its special forces walked inside a gas pipeline to strike Ukrainian units from the rear in the Kursk region as Moscow claimed fresh gains in its push to recapture parts of the border province that Kyiv seized. The surprise strike on its forces was confirmed by the Ukrainian military, reports said.

According to Telegram posts late Saturday by a Ukrainian-born, pro-Kremlin blogger, Russian operatives walked about 15 kilometers (9 miles) inside the pipeline, which Moscow had until recently used to send gas to Europe. Some Russian troops spent several days in the pipe before striking Ukrainian units from the rear near Sudzha, blogger Yuri Podolyaka claimed.

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Another war blogger, who uses the alias Two Majors, said fierce fighting was underway for Sudzha, and that Russian forces managed to enter the town through a gas pipeline. Russian Telegram channels showed photos of what they said were special forces operatives, wearing gas masks and moving along what looked like the inside of a large pipe.

Ukraine's General Staff confirmed Saturday evening that Russian sabotage and assault groups used the pipeline in a bid to gain a foothold outside Sudzha. In a Telegram post, it said Russian troops were detected in a timely manner and that Ukraine responded with rockets and artillery.

Meanwhile, Moscow said that its troops had taken four villages north and northwest of Sudzha, with the closest lying some 12 kilometres (7.5 miles) from the centre of the town. The claim came a day after the ministry reported the capture of three more villages near Sudzha.

Ukraine did not immediately comment on the Russian claims, the US news agency said.

Battlefields of Kursk Oblast

Ukraine launched a daring cross-border incursion into Kursk in August, marking the largest attack on Russian territory since World War II. Within days, Ukrainian units had captured 1,000 square kilometres of territory, including the strategic border town of Sudzha, and taken hundreds of Russian prisoners of war.

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According to Kyiv, the operation aimed to gain a bargaining chip in future peace talks and to force Russia to divert troops away from its grinding offensive in eastern Ukraine.

However, tides seem to have turned in the contested Russian territory as Ukrainian soldiers in the region are hit hard by relentless assaults by Russian and North Korean troops who number above 50,000. Tens of thousands of Ukrainian soldiers are at risk of being encircled,  news agency Associated Press said.